The present invention relates to a waste treatment system, and more particularly to a waste treatment system for processing human waste on boats, recreational vehicles, and other remote toilet facilities where traditional sewers and septic systems are impractical or unavailable.
Waste treatment systems designed for use with toilets in remote or portable facilities such as in vehicles, aircraft, watercraft, and railroad cars must ultimately dump collected waste to another system or to the environment. In some known systems the waste is merely accumulated in large tanks and pumped off for processing elsewhere when the boat or other vehicle reaches a waste receiving station. See for example U.S. Pat. No. 4,324,007. However, it is desirable to discharge the waste into the environment when it is not practical to hold the amounts of waste that will accumulate before a collection station can be reached. But government regulations prohibit discharging of raw human bodily waste directly into the environment because the raw waste has bacteria, particularly fecal coliform bacteria, that may pose a health hazard in excess concentration.
For example, in the case of watercraft, federal regulations (33 C.F.R. .sctn. 159) require that human waste discharged into the water from boats in certain circumstances have a live fecal coliform bacteria count of not greater than 1,000 bacteria per 100 milliliters of discharge and no visible floating solids. Marine waste treatment systems that meet these standards are generally called "Type I" devices. In certain circumstances, the discharged waste, or "effluent," is required to have a fecal coliform bacteria count not greater than 200 parts per 100 milliliters and suspended solids not greater than 150 milligrams per liter. Marine waste systems that meet this standard are called "Type II" devices.
In other known systems, the raw waste is collected in a tank and treated in that tank prior to discharge of the tank contents to the environment. The tank can then accept more waste. See for example U.S. Pat. No. 5,433,842. Typically, these known types of waste treatment systems employ large holding tanks that receive raw waste directly from the toilets. The holding tanks include heaters that heat the collected waste to a temperature above about 155.degree. Fahrenheit to kill fecal coliform bacteria. These known sewage treatment systems suffer from a disadvantage in that the holding tanks are very large, 40 gallons or more, and require a substantial amount of time and energy to heat the collected waste to a sufficient temperature to kill the fecal coliform bacteria. Moreover, as the waste in the tank is being heated, new waste piped in from the toilets cools the waste and causes further delays. If the tank fills before the water has rendered a sufficient temperature to kill the coliform bacteria, then the toilet cannot be used until the processing is finished. Moreover, placement of the large tank can be difficult in uses where there is limited space, such as on boats and other vehicles.
Accordingly, there is a need in the art for waste treatment systems for remote facilities that eliminate fecal coliform bacteria and visible solids from human waste in a manner which conserves space and energy resources.